Varnishing Tips

Generally speaking, you would probably be better off using a simple polyurethane. You will need to rub down past any nasties like crackling and get rid of those "black" areas. Use your finger tips to feel for uneveness or roughness. You should use a block such as a rubber one from DIY/Car stores, bare hands will cause uneven pressure on the glasspaper and will lead to a grotty looking finish. Use your finger tips to *see* the surface.

Gradually, build up the varnish layers over the areas that received the most attention with the glasspaper. Use *thin* layers and let each one dry thoroughly before applying the next. Rub each surface down gently with progressively finer grades of glasspaper for each layer and look with your hands.

When applying varnish to bare/new wood, use a mix of 50% varnish, 50% white spirit. This will soak into the wood and cause a lot of fibre ends to stand up. It looks very rough but when you sand it down gently with a block and paper you will get a much smoother finish for the subsequent layers of varnish. Apply up to 3 further thin layers, only gently brushing in the direction of the grain.

For a professional finish on the topcoat, you must use a paintbrush that a) won't loose it's bristles and b) has very long bristles of about 5"/125mm. This means that the brush is going to be expensive but it will be worth it. Only gently brush along the lines of the grain and use as few a number of brush strokes as possible. Finally you need to "lay-off" the varnish. Hold the brush at a shallow an angle as possible and very, very gently stroke the brush along the grain.

Have a practice on a spare piece or wood and see what result you can achieve, you will be amazed how easy it really is. It only  takes patience and very gentle brushwork - Go luck!

ooh can i join this, what's the best way of gettnig old varnish off? And what concentration of paint thinner to varnish do you need if it's on bare wood?

What do want to varnish? There are different techniques depending on what you are trying to achieve, not to mention different varnishes.